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Calculator · Gearing

Gearing Calculator

Enter your sprocket teeth, tire size and engine specs to get your final drive ratio and estimated top speed, then compare nearby sprocket combinations.

Your Setup

Typical MX/enduro rear (110/90-19) ≈ 28.4". Check your tire's sidewall or manufacturer spec if unsure.

Combined top-gear and primary reduction, listed in most owner's/service manuals. 4.9 is a common 450 MX top-gear approximation — replace with your bike's actual figure for an accurate result.

Final Drive Ratio

Estimated Top Speed

mph

Estimate only — actual top speed varies with engine tune, wind resistance, terrain and rider weight.

Nearby Rear Sprocket Options

Rear TeethRatioTop SpeedEffect

How This Works

Your final drive ratio is simply rear sprocket teeth divided by front sprocket teeth. A bigger rear (or smaller front) lowers your gearing — quicker acceleration, lower top speed, better for tight technical trail. A smaller rear (or bigger front) raises your gearing — higher top speed, less low-end snap, better for fast open terrain.

Top speed is estimated from your engine RPM, tire diameter, and total drivetrain reduction (final drive ratio × internal gearbox/primary ratio). Adding or removing even one or two teeth on the rear sprocket can shift top speed and acceleration noticeably — the comparison table above shows how nearby options stack up against your current setup.

This is a planning estimate, not a dyno-verified number — always confirm chain length compatibility before swapping sprockets, and re-torque your rear axle and chain adjusters after any gearing change.